Solubility of a gas in liquid, Raoult's law and Ideal and non-ideal solutions - Lesson Summary

Gases dissolve in liquids to form solutions.

The dissolution of gases in liquids is an equilibrium process. At equilibrium, the rate at which the gaseous solute molecules escape the solution equals the rate at which the molecules re-enter the solution.

An increase in pressure results in more molecules of the gas striking the surface of the liquid and entering the solution in a given time.

Therefore, at high pressure, more gas dissolves in a given volume of liquid than at lower pressures.

This proportionality of the solubility of a gas to pressure was first proposed by William Henry, and is known as Henry's law.

Henry's law:

The law states that at a constant temperature, the solubility of a gas in a liquid is directly proportional to the pressure of the gas.

The most commonly used version of Henry's law is: "The partial pressure of a gas in vapour phase (p) is proportional to the mole fraction of the gas (χ) in a solution."

p ∝ χ

p =KH χ

Where KH = Henry's law constant.

Plot a graph between p, the partial pressure of a gas in vapour phase, and χ the mole fraction of the gas in a solution, then you will get a straight line passing through the origin.

The graph also shows that as p increases, χ the mole fraction of the gas in a solution, also increases.

Applications of Henry's law:

This law used in the preparation of carbonated drinks.

Henry's law has an important application for scuba divers. Scuba divers experience bends problem.to overcome this problem Henry's law is utilized.

Mountaineers at high altitude suffer from anoxia. This problem is also overcome by applying Henry's law.

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